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An executive of Drivers.com recently bought four used tires from a dealer and was told to keep the pressure four psi (pounds per square inch) higher in winter than in summer. Not so.

Reader's comments below

At a time when tires are making the headlines every day because of the Firestone controversy, this anecdote only serves to illustrate how much misinformation is circulating about tires and their care and maintenance.

Other myths about tire inflation include keeping the pressure lower in winter than in summer; and that the best time to check tire pressure is after a long trip.

In fact, tire pressure usually lowers itself in winter and raises itself in summer-it requires no action on the part of the motorist apart from keeping the pressure at the level recommended on the sticker that is usually located just inside the door, glove box, or fuel door. Under normal loads, inflate tires according to the vehicle manufacturer's recommendations, NOT the maximum pressure listed on the sidewall. In any case, one should never exceed this maximum pressure.

The sidewall, incidentally, also shows the type of cord and number of plies in the sidewall and under the tread.

Every time the outside temperature drops 10 degrees Fahrenheit, the air pressure inside your tires goes down about one or two psi. Drivers should check their tire pressures frequently during cold weather, adding enough air to keep them at recommended levels of inflation at all times.

Another winter no-no, according to the tire experts, is never reduce tire pressures in an attempt to increase traction on snow or ice. It does not work and your tires will be so seriously under-inflated that driving will damage them.

One of the warnings issued by Bridgestone/Firestone and Ford after it was revealed that defective tires may be linked to as many as 88 deaths and 1,400 crashes was that under-inflated tires are likely to overheat and burst. So, if there's any silver lining to these tragedies, it's that they've drawn attention to a potentially deadly traffic hazard.

However, it's important to get the facts straight.

An invaluable resource in this respect is the Tire Industry's Safety Council , which publishes a free 18-page brochure on the latest in tire care. This brochure has safety information for cars and light trucks, including information on proper tire inflation, safety warnings, tire rotation, vehicle conditions affecting tires, speed ratings, replacement tire selection, and tips on cold weather driving. The information is also available on the council's web site.

Among the many useful hints and tips, the council recommends that drivers have their own pressure gauge. "Tires must be properly inflated," the council says. "Use an accurate tire pressure gauge to determine your tire pressure. You can't tell when tires are 'low,' or under-inflated, just by looking. Air meters at service stations may be inaccurate due to exposure or abuse. You should have your own personal tire gauge to be sure."

The council also advises drivers to check their tire inflation pressure (including the spare) at least once a month, and before every long trip.

"Tires must be checked when they are cold; that is, before they have been run a mile. If you must drive over one mile for air, before you leave home, measure the cold inflation pressure of each tire and record the actual under-inflation amount for each tire.

"Upon arriving at the service station, measure each tire's inflation again and then inflate the warm tire to a level that is equal to this warm pressure, plus the cold under-inflation amount."

Tires lose air normally through the process of permeation, the council says. "Changes in outdoor temperature can affect the rate at which your tire loses air. This change is more pronounced in hot weather. Generally speaking, a tire will lose one or two pounds of air per month in cool weather, and even more in warmer weather. Under-inflation is the leading cause of tire failure, so check inflation pressure regularly.

"Never "bleed" or reduce air pressure when tires are hot. It is normal for pressure to build up as a result of driving.

"Make sure all tire valves and extensions are equipped with valve caps with rubber gaskets to keep out dirt and moisture. Have a new valve stem assembly installed whenever a tire is replaced.

"Under-inflation or overloading creates excessive heat," the council warns, "and can lead to tire failure, which could result in vehicle damage and/or serious injury or death. Proper inflation extends tire life and saves fuel."

In North America, regulations require tire manufacturers to grade passenger car tires based on three performance factors: treadwear, traction, and temperature resistance.

The treadwear grade is a comparative rating based on the wear rate of the tire when tested under controlled conditions on a specified government test track. A tire graded 200, for example, would wear twice as long on the government test course under specified test conditions as one graded 100.

It is wrong to link treadwear grades with your projected tire mileage. The relative performance of tires depends upon the actual conditions of their use and may vary due to driving habits, service practices, differences in road characteristics, and climate.

Traction grades, from highest to lowest, are A, B, and C. They represent the tire's ability to stop on wet pavement as measured under controlled conditions on specified government test surfaces of asphalt and concrete.

The temperature grades, from highest to lowest, are A, B, and C. These represent the tire's resistance to the generation of heat.

Related links:

• Firestone recall: certain tires may be dangerous
• Faulty tire saga picks up steam
• Clearing up confusion over snow tires
  

Reader's Comment

Bob Joynt:
As an instructor and owner of Control Driving Skills in Smiths Falls, Canada, our classes are taught to keep their tires at the "Maximum" air pressure indicated on the sidewall at all times for safety and vehicle control reasons.... more

Discuss this article

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Comments

Ileana, on Tuesday, 14. August 2007 at 01:14 PM

nate, on Saturday, 08. December 2007 at 08:44 AM

Jennifer, on Saturday, 19. January 2008 at 10:59 AM

Dot, on Saturday, 05. July 2008 at 10:46 PM

DK, on Monday, 07. July 2008 at 10:24 AM

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